Fertility potential and safety assessment of residual ovarian cortex in young women diagnosed with epithelial borderline and early-stage malignant ovarian tumors

OBJECTIVE

To establish the safety and quality of ovarian cortex surrounding epithelial ovarian tumors in women eligible for fertility-sparing surgery by identifying occult malignant lesions and characterizing the ovarian follicle pool.

METHODS

Multicentric retrospective study of 48 subjects (15-45 years), diagnosed with borderline ovarian tumors (BOTs) or early-stage epithelial ovarian cancers (EOCs) and eligible for fertility-sparing surgery. Histological samples of ovarian cortex surrounding tumors were analyzed to characterize the follicle pool, find any occult malignant lesion using tumor-specific markers (cytokeratin 7 and mucin 1), and quantify tumor-infiltrating lymphocytes (TILs) by CD3 and tumor associated macrophages (TAMs) by CD68.

RESULTS

Occult ovarian lesions were observed in 6 out of 45 cases investigated (14.6%), including one mucinous stage-I BOT (1/14), one serous stage-I BOT (1/13), 3 advanced-stage serous BOTs (3/11) and one early-stage serous EOC (1/7). Notably, follicle density was significantly lower in subjects diagnosed with ovarian tumors compared to controls (p < 0.001) and at a younger age. Significantly higher follicle atresia was encountered in the ovarian tumor group then in controls (20.1 ± 8.8% vs 9.2 ± 9.4%, p < 0.001) at all ages. Both TILs and TAMs were found in ovarian tumors irrespective of histotype, but no link was established with the status of the ovarian reserve.

CONCLUSIONS

Personalized counseling for fertility preservation is required in the event of BOTs and early-stage EOCs. Fertility-sparing surgery and adjuvant gamete preservation should be considered, balancing the oncological risks according to tumor stage and histotype and fertility potential, especially at a younger age.

Impact of human ovarian tissue manipulation on follicles: evidence of a potential first wave of follicle activation during fertility preservation procedures

PURPOSE

The aim of this study was to investigate the impact of processing human ovarian tissue on follicle activation dynamics.

METHODS

Fresh ovarian tissue was retrieved from 9 women undergoing laparoscopic surgery for benign conditions. Biopsies from each patient were divided into 3 fragments, the first of which was immediately fixed in the operating room (T0) and the second and third just after processing at 25 (T25) and (T90) 90 min. To evaluate follicle activation, markers of the PI3K and Hippo signaling pathways were immunolabeled at each time point, targeting phospho-Akt (p-Akt) by immunohistochemistry and yes-associated protein (YAP) cellular localization in the granulosa cell layer by immunofluorescence.

RESULTS

Four hundred forty primordial follicles were evaluated for p-Akt and 420 for YAP. Significantly stronger p-Akt expression was observed at T25 (23.01 ± 13.45%; p=0.04) and T90 (38.99 ± 25.21%; p<0.001) than at T0 (2.72 ± 3.35%). A significant nucleus-to-cytoplasm shift in YAP was detected at T25 (1.21 ± 0.25; p=0.015 compared to T0 (0.95 ± 0.09), while T90 (1.10 ± 0.16) values were similar to T25.

CONCLUSION

Our data prove that ovarian tissue manipulation significantly impacts follicle dynamics by stimulating the PI3K and Hippo signaling pathways involved in primordial follicle activation. Further experimental evidence must nevertheless be gathered to understand and gain control of follicle activation mechanisms in non-physiological conditions (like ovarian tissue manipulation), in order to optimize fertility preservation and restoration strategies.

Use of mesenchymal stem cells to enhance or restore fertility potential: a systematic review of available experimental strategies

STUDY QUESTION

To what extent does regenerative medicine with stem cell therapy help to address infertility issues for future clinical application?

SUMMARY ANSWER

Regenerative medicine using different stem cell sources is yielding promising results in terms of protecting the ovarian reserve from damage and senescence, and improving fertility potential in various preclinical settings.

WHAT IS KNOWN ALREADY

Regenerative medicine using stem cell therapy is emerging as a potential strategy to address a number of issues in the field of human reproduction. Indeed, different types of adult and fetal mesenchymal stem cells (MSCs) have been tested with promising results, owing to their ability to differentiate into different tissue lineages, move toward specific injured sites (homing), and generate a secretome with wound-healing, proangiogenic, and antioxidant capacities.

STUDY DESIGN SIZE DURATION

Guided by the checklist for preferred reporting items for systematic reviews and meta-analyses, we retrieved relevant studies from PubMed, Medline, and Embase databases until June 2023 using the following keywords: 'mesenchymal stem cells' AND 'ovarian follicles' OR 'ovarian tissue culture' OR 'ovarian follicle culture' OR 'cumulus oocyte complex'. Only peer-reviewed published articles written in English were included.

PARTICIPANTS/MATERIALS SETTING METHODS

The primary outcome for the experimental strategies was evaluation of the ovarian reserve, with a focus on follicle survival, number, and growth. Secondary outcomes involved analyses of other parameters associated with the follicle pool, such as hormones and growth factors, ovarian tissue viability markers including oxidative stress levels, oocyte growth and maturation rates, and of course pregnancy outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

Preclinical studies exploring MSCs from different animal origins and tissue sources in specific conditions were selected (n = 112), including: in vitro culture of granulosa cells, ovarian tissue and isolated ovarian follicles; ovarian tissue transplantation; and systemic or intraovarian injection after gonadotoxic or age-related follicle pool decline. Protecting the ovarian reserve from aging and gonadotoxic damage has been widely tested in vitro and in vivo using murine models and is now yielding initial data in the first ever case series of patients with premature ovarian insufficiency. Use of MSCs as feeder cells in ovarian tissue culture was found to improve follicle outcomes and oocyte competence, bringing us one step closer to future clinical application. MSCs also have proved effective at boosting revascularization in the transplantation site when grafting ovarian tissue in experimental animal models.

LIMITATIONS REASONS FOR CAUTION

While preclinical results look promising in terms of protecting the ovarian reserve in different experimental models (especially those in vitro using various mammal experimental models and in vivo using murine models), there is still a lot of work to do before this approach can be considered safe and successfully implemented in a clinical setting.

WIDER IMPLICATIONS OF THE FINDINGS

All gathered data on the one hand show that regenerative medicine techniques are quickly gaining ground among innovative techniques being developed for future clinical application in the field of reproductive medicine. After proving MSC effectiveness in preclinical settings, there is still a lot of work to do before MSCs can be safely and effectively used in different clinical applications.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS-PDR T.0077.14, FNRS-CDR J.0063.20, and grant 5/4/150/5 awarded to Marie-Madeleine Dolmans), Fonds Spéciaux de Recherche, and the Fondation St Luc. None of the authors have any competing interest to disclose.

REGISTRATION NUMBER

N/A.

The Chick Chorioallantoic Membrane (CAM) Model as a Tool to Study Ovarian Tissue Transplantation

Ovarian tissue cryopreservation and transplantation is an effective strategy for preserving fertility but has one major drawback, namely massive follicle loss occurring shortly after reimplantation due to abnormal follicle activation and death. Rodents are benchmark models for investigating follicle activation, but the cost, time, and ethical considerations are becoming increasingly prohibitive, thus driving the development of alternatives. The chick chorioallantoic membrane (CAM) model is particularly attractive, being inexpensive and maintaining natural immunodeficiency up to day 17 postfertilization, making it ideal to study short-term xenografting of human ovarian tissue. The CAM is also highly vascularized and has been widely used as a model to explore angiogenesis. This gives it a remarkable advantage over in vitro models and allows the investigation of mechanisms affecting the early post-grafting follicle loss process. The protocol outlined herein aims to describe the development of a CAM xenografting model for human ovarian tissue, with specific insights into the effectiveness of the technique, the graft revascularization time frame, and the tissue viability across a 6 day grafting period.

Importance of oxygen tension in human ovarian tissue in vitro culture

STUDY QUESTION

Is there any difference between 20% and 5% oxygen (O2) tension in vitro culture (IVC) on the viability and quality of human follicles contained in cultured ovarian cortex?

SUMMARY ANSWER

An O2 tension of 5% yields higher follicle viability and quality than does 20% O2 tension after 6 days of IVC.

WHAT IS KNOWN ALREADY

The primordial follicle (PMF) pool resides within the ovarian cortex, where the in vivo O2 tension ranges between 2% and 8%. Some studies suggest that lowering O2 tension to physiological levels may improve in vitro follicle quality rates.

STUDY DESIGN, SIZE, DURATION

This prospective experimental study included frozen-thawed ovarian cortex from six adult patients (mean age: 28.5 years; age range: 26-31 years) who were undergoing laparoscopic surgery for non-ovarian diseases. Ovarian cortical fragments were cultured for 6 days at (i) 20% O2 with 5% CO2 and (ii) 5% O2 with 5% CO2. Non-cultured fragments served as controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cortical fragments were used for the following analyses: hematoxylin and eosin staining for follicle count and classification; Ki67 staining to evaluate PMF proliferation; cleaved caspase-3 immunostaining to identify follicle apoptosis; 8-hydroxy-2-deoxyguanosine and gamma-H2AX (γH2AX) immunolabeling to detect oxidative stress damage and DNA double-strand breaks (DSBs) in oocytes and granulosa cells (GCs); and β-galactosidase staining to assess follicle senescence. Droplet digital PCR was also performed to further explore the gene expression of superoxide dismutase 2 (SOD2) and glutathione peroxidase 4 (GPX4) from the antioxidant defense system and cyclin-dependent kinase inhibitors (p21 and p16) as tissue senescence-related genes.

MAIN RESULTS AND THE ROLE OF CHANCE

Apoptosis (P = 0.002) and follicle senescence (P < 0.001) rates were significantly lower in the 5% O2 group than in the 20% O2 group. Moreover, GCs in follicles in the 20% O2 group exhibited significantly (P < 0.001) higher oxidative stress damage rates than those in the 5% O2 group. DNA DSB damage rates in GCs of follicles were also significantly higher (P = 0.001) in the 20% O2 group than in the 5% O2 group. SOD2 expression was significantly greater in the 5% O2 group compared to the 20% O2 group (P = 0.04) and the non-cultured group (P = 0.002). Expression of p21 was significantly increased in both the 20% O2 (P = 0.03) and 5% O2 (P = 0.008) groups compared to the non-cultured group. Moreover, the 20% O2 group showed significantly greater p16 expression (P = 0.04) than the non-cultured group, while no significant variation was observed between the 5% O2 and no culture groups.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This study focuses on improving follicle outcomes during the first step of ovarian tissue IVC, where follicles remain in situ within the tissue. The impact of O2 tension in further steps, such as secondary follicle isolation and maturation, was not investigated here.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that 5% O2 tension culture is a promising step toward potentially solving the problem of poor follicle viability after IVC.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS-PDR T.0064.22, CDR J.0063.20 and grant 5/4/150/5 awarded to M.M.D.). The authors have nothing to disclose.

Profile of Linzagolix in the Management of Endometriosis, Including Design, Development and Potential Place in Therapy: A Narrative Review

Estrogens play a critical role in the pathogenesis of endometriosis and it is logical to assume that lowering estradiol levels with oral gonadotropin-releasing hormone (GnRH) antagonists may prove effective, especially in women who fail to respond to progestogens. Indeed, due to progesterone resistance, oral contraceptives and progestogens work well in two-thirds of women suffering from endometriosis, but are ineffective in 33% of women. Oral GnRH antagonists have therefore been evaluated for management of premenopausal women with endometriosis-associated pelvic pain. The first publication on these drugs reported the efficacy of elagolix. The present paper is a narrative review of linzagolix, which is an orally administered GnRH receptor antagonist with low pharmacokinetic/pharmacodynamic variability. It binds to and blocks the GnRH receptor in the pituitary gland, resulting in a dose-dependent drop in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) production. This reduction in LH and FSH levels in turn leads to a dose-dependent decline in estrogen. Phase 2 and 3 trials are reviewed and discussed here. There is a place for GnRH antagonists in the management of symptomatic endometriosis, and linzagolix with or without add-back therapy (ABT) is one option that can be used at low doses, avoiding the need for ABT, which is contraindicated in some patients.

Role of apoptosis and autophagy in ovarian follicle pool decline in children and women diagnosed with benign or malignant extra-ovarian conditions

STUDY QUESTION

Which biological mechanisms are responsible for physiological ovarian reserve decline owing to aging, or pathological follicle depletion triggered by inflammation or a pro-oxidant environment throughout a woman's lifetime?

SUMMARY ANSWER

Ovarian follicle pool size is modulated by both apoptosis and autophagy, the first responsible for its physiological decline over time and increasing in the event of prior chemotherapy in children, and the latter playing a major role in physiological ovarian follicle pool diminution before puberty.

WHAT IS KNOWN ALREADY

Among the different pathways of controlled cell death, apoptosis and autophagy are implicated in follicle loss. Apoptosis participates in eliminating damaged follicles, such as those impaired by chemotherapy (CHT), but its involvement in physiological age-related follicle decline is less well understood. Autophagy has proved crucial in follicle quiescence maintenance in murine models, but its contribution to human follicle pool modulation is still unclear.

STUDY DESIGN, SIZE, DURATION

This retrospective study included 84 patients with benign or malignant extra-ovarian conditions aged between 1 and 35 years, with ovarian tissue stored for histological analyses at the time of cryopreservation (between 2012 and 2021) at a tertiary care center.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ovarian fragments were used for the following analyses: hematoxylin and eosin staining for follicle count and classification; cleaved caspase-3 immunostaining to identify follicle apoptosis; and microtubule-associated proteins 1A/1B light chain 3B immunolabeling to detect follicle autophagy. Transmission electron microscopy was also carried out to investigate ultrastructural features of oocytes and granulosa cells. All analyses stratified patients by age, menarchal status (premenarchal = 32; postmenarchal = 52), potentially gonadotoxic CHT before cryopreservation (n = 14), presence of endometriosis and use of hormonal treatment.

MAIN RESULTS AND THE ROLE OF CHANCE

Premenarchal patients had a larger follicle pool in terms of total follicle density [mean, range 4979.98 (342.2-21789) versus 918.8 (26.18-3983), P < 0.001], but higher rates of morphologically abnormal [8.52 (0-25.37)% versus 3.54 (0-17.5)%, P < 0.001] and atretic [15.8 (0‒31.85)% versus 10.6 (0-33.33)%, P < 0.01] follicles than postmenarchal subjects. Apoptosis rates did not change with increasing age [27.94 (0-93.2)% in prepubertal subjects and 29.5 (0-100)% in postpubertal subjects], but autophagic follicles were around 10 times more common in premenarchal than postmenarchal subjects [10.21 (0-62.3)% versus 1.34 (0-25)%, P < 0.001], playing a crucial role in age-related follicle decline and elimination of 'abnormal' follicles, that are rarely seen after menarche. The impact of diagnosis and previous CHT varied according to age. In premenarchal patients with previous CHT, significantly more apoptotic [40.22 (0-100)% versus 26.79 (0-87)%, P < 0.05] and fewer abnormal [3.84 (0-10-76)% versus 9.83 (0-25.37)%, P < 0.01] follicles were detected than in subjects with no CHT prior to ovarian tissue cryopreservation, suggesting a direct effect on follicle elimination, especially of those with abnormalities. In postmenarchal subjects with previous CHT, quiescent follicle rates were lower than in patients with no CHT before tissue freezing [71.57 (0-100)% versus 85.89 (50-100)%, P < 0.05], suggesting accelerated follicle activation and growth. Moreover, increased autophagic activity was observed in the event of a cancer diagnosis compared to benign conditions after puberty [26.27 (0-100)% versus 9.48 (0-29.41)%, respectively, P < 0.05].

LIMITATIONS, REASONS FOR CAUTION

The impact of specific CHT protocols could not be investigated since the group of patients with previous CHT was highly heterogeneous.

WIDER IMPLICATIONS OF THE FINDINGS

This study yields a deeper understanding of regulation of the follicle pool decline, showing for the first time that both apoptosis and autophagy pathways are involved in physiological follicle depletion, the latter being crucial before puberty. Moreover, our data showed a different response to non-physiological damage according to age, with higher apoptosis rates only in premenarchal subjects with previous CHT, confirming that this pathway is activated by drugs known to induce DNA damage in oocytes, such as alkylating agents, but not by cancer itself.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (F.R.S.-FNRS/FRIA FC29657 awarded to L.C., CDR J.0063.20 and grant 5/4/150/5 awarded to M.M.D.), grants from the Fondation contre le Cancer (grant 2018-042 awarded to A.Ca.), the Fondazione Comunitaria del Varesotto and Provincia di Varese ('Amalia Griffini' Fellowship in Gynecology and Obstetrics awarded to A.Ce.), Fonds Spéciaux de Recherche, Fondation St Luc and donations from the Ferrero family. The authors have no competing interests to declare.

TRIAL REGISTRAION NUMBER

N/A.

Follicle outcomes in human ovarian tissue: effect of freezing, culture, and grafting

OBJECTIVE

To study the effect of freezing, in vitro culture (IVC) and grafting to chorioallantoic membrane (CAM) on follicle outcomes in human ovarian tissue.

DESIGN

An experimental study.

SETTING

University-based research laboratory.

PATIENTS

Fresh and cryopreserved ovarian tissue from 10 patients was donated to research with their consent and institutional review board approval.

INTERVENTIONS

Fresh and frozen-thawed ovarian cortical pieces were in vitro-cultured and compared (fresh-IVC vs FT-IVC). The FT-IVC fragments were then examined against fragments grafted to CAM (FT-CAM). After both IVC and CAM grafting, ovarian cortical pieces (4×2×1 mm³) were analyzed on days 0, 1, and 6.

MAIN OUTCOME MEASURES

Follicle analyses included histology (count and classification) and immunohistochemistry (Ki67 [proliferation], caspase-3 [apoptosis], 1A and 1B light chain 3B [autophagy], p-Akt, FOXO1, and p-rpS6 [PI3K activation]). Droplet digital polymerase chain reaction further explored expression of PI3K pathway- and oocyte-related genes in tissue sections.

RESULTS

No major differences were detected between fresh-IVC and FT-IVC tissues in any conducted analyses. Although a significant drop was observed in primordial follicle (PF) proportions in the fresh-IVC and FT-IVC groups (d0 vs. d6, P<.002), they held steady in the FT-CAM group (d0 vs. d6, P>.05). The PF rates were also significantly higher in the FT-CAM group than the FT-IVC group on d6 (P=.02). Importantly, avian erythrocytes were already present in 30% of implants from d1. Apoptotic and autophagic follicle rates increased during IVC (P<.008), but remained significantly lower in the FT-CAM group (P<.01), confirming superior follicle preservation in CAM-grafted tissue. Upregulation of the PI3K/FOXO pathway was established in the IVC groups, demonstrating PF activation, whereas significant pathway downregulation was detected in the FT-CAM group (P<.03). The droplet digital polymerase chain reaction tests confirmed oocyte growth during IVC and follicle autophagy in all groups; however, the PI3K pathway appeared to be differentially modulated in tissues and follicles.

CONCLUSIONS

In vitro culture induces PF depletion with no additional impact of freezing. Grafting to CAM preserves the PF pool by curbing follicle activation, apoptosis, and autophagy, probably thanks to rapid graft revascularization and/or the circulating embryonic antimüllerian hormone. These findings highlight the importance of enhancing neoangiogenesis in ovarian grafts and investigating the potential benefits of administering antimüllerian hormone to prevent PF burnout.

A synopsis of the 2021 International Society of Fertility Preservation bi-annual meeting

On November 19, 2021, the first virtual meeting of the International Society for Fertility Preservation (ISFP) took place. Eight experts in the field of reproductive medicine presented important updates on their research in the field of fertility preservation and reproductive surgery for absolute uterine factor infertility. Presentations included talks on ovarian stem cell therapy for premature ovarian insufficiency, practical aspects of oocyte vitrification, ovarian stimulation for patients with breast cancer, in vitro maturation of oocytes at the time of ovarian tissue harvesting, male fertility preservation, and uterine transplantation. These presentations are summarized below and can be viewed in their entirety at www.isfp-fertility.org.

O-038 Role of apoptosis and autophagy in ovarian follicle pool decline from birth to late reproductive age and after gonadotoxic chemotherapeutic treatments

Study question

Which biological mechanisms are responsible for physiological age-dependent and non-physiological ovarian reserve decline throughout a woman’s life?

Summary answer

Ovarian follicle pool size is modulated by both apoptosis and autophagy, the latter playing a major role in its decline before puberty.

What is known already

Among different pathways of controlled cell death, apoptosis and autophagy are both involved in follicle death. Apoptosis participtes in eliminating damaged follicles, like those affected by chemotherapy (CHT)-induced DNA damage, but its role in physiological age-related follicle decline is less understood. Autophagy has proved crucial in follicle quiescence maintenance in murine models, but its contribution to human follicle pool modulation is still unclear.

Study design, size, duration

Eighty-four patients aged between 1 and 35 years, with ovarian tissue stored for histological analyses at the time of cryopreservation (between 2012 and 2021) at the Université Catholique de Louvain (Belgium) were included in retrospective evaluations.

Participants/materials, setting, methods

Ovarian fragments were used for the following analyses: hematoxylin and eosin staining for follicle count and classification; caspase-3 immunostaining to identify follicle apoptosis; and microtubule-associated proteins 1A/1B light chain 3B (LC3B) immunolabeling to detect follicle autophagy. Ovarian fragments from 9 patients were assigned for transmission electron microscopy to investigate ultrastructural features of oocytes and granulosa cells. All analyses were conducted stratifying patients by age, menarchal status (premenarchal=32; postmenarchal=52), and potentially gonadotoxic CHT before cryopreservation (n = 14).

Main results and the role of chance

Premenarchal patients had a larger follicle pool in terms of total follicle density (4979.98±4952.16 vs 918.8±903.86, p &lt; 0.0001), but higher rates of morphologically abnormal (8.52±6.48% vs 3.54±4.54%, p &lt; 0.0001) and atretic follicles (15.8±9.14% vs 10.6±9.43%, p = 0.01) than postmenarchal subjects. Apoptosis rates did not change with increasing age (27.94±28.78% in prepubertal subjects and 29.5±33.58% in postpubertal subjects). Autophagic follicles were around 10 times more common in premenarchal compared to postmenarchal subjects (10.21±16.% vs 1.34±4.02%, p &lt; 0.0001), playing a crucial role in age-related follicle decline and elimination of ‘abnormal follicles’, that are rarely seen after menarche. The impact of previous CHT varied according to age. In premenarchal patients with previous CHT, significantly more apoptotic (40.22±40.44% vs 26.79±25.35%, p = 0.04) and fewer abnormal (3.84±3.91% vs 9.83±6.5%, p = 0.02) follicles were detected than in those with no CHT prior to ovarian tissue cryopreservation, suggesting a direct effect on follicle elimination, especially of those with abnormalities. In postmenarchal subjects with previous CHT, lower quiescent follicle rates were observed compared to patients with no CHT before tissue freezing (70.1±36.36% vs 85.89±12.61%, p = 0.04), suggesting accelerated follicle activation and growth.

Limitations, reasons for caution

The present study could not investigate the impact of specific CHT protocols, since the group of patients with previous CHT was highly heterogeneous. However, these patients could not be excluded a priori, since the effect of follicle pool depletion has not been fully elucidated.

Wider implications of the findings

This study yields a deeper understanding of follicle pool decline regulation, evidencing for the first time that (i) different cell death pathways are involved in physiological and non-physiological follicle depletion, and (ii) the follicle pool responds differently to gonadotoxic damage according to age and ovarian reserve size.

Trial registration number

N/A

P-437 Follicle activation in human ovarian tissue: impact of freezing, culture and grafting

Study question

How does freezing, in vitro culture (IVC) and grafting to chorioallantoic membrane (CAM) affect follicle activation through the PI3K pathway in human ovarian tissue?

Summary answer

Freezing does not trigger further follicle activation. Although IVC and CAM do induce follicle activation, the process is significantly curbed in the CAM group.

What is known already

While massive follicle activation has been shown to occur through the PI3K pathway in frozen-thawed human ovarian tissue after both short-term xenotransplantation and IVC, it remains poorly understood in fresh ovarian tissue, raising many questions about the effect of freezing on follicle activation. Furthermore, grafting ovarian tissue to CAM has been found to limit follicle activation in animal ovarian tissue, though its impact on human follicles is yet to be elucidated.

Study design, size, duration

Thirty fresh cortical fragments from 5 patients and 50 frozen-thawed tissue pieces from another 5 patients were investigated. We first compared fresh fragments (fresh-IVC) with frozen-thawed tissue (FT-IVC) by IVC. These cultured frozen-thawed fragments were then examined against frozen-thawed fragments grafted to CAM (FT-CAM). After both IVC and CAM grafting, ovarian cortical pieces (4x2x1 mm) were analyzed on day (D) 0, 1 and 6.

Participants/materials, setting, methods

Follicle analyses included histology (count and classification), transmission electron microscopy (ultrastructure), immunohistochemistry (Ki67 for follicle proliferation, c-caspase-3 for follicle apoptosis, LC3B for follicle autophagy, p-AKT for PI3K activation and p-rpS6 for PI3K/mTOR activation), and immunofluorescence (FOXO1 for PI3K/FOXO activation). Subcellular localization of FOXO1 was determined in primordial follicles on high-resolution images using structured illumination microscopy. Droplet digital PCR further investigated expression of PI3K pathway-related genes (TSC1 and CDKN1B) and oocyte growth-related genes (GDF9 and LHX8).

Main results and the role of chance

No differences were detected between the fresh-IVC and the FT-IVC groups in any conducted analyses. After both IVC and CAM grafting, a significant decrease was observed in primordial follicle proportions in all groups on D6 vs D0 (p &lt; 0.01), associated with a substantial increase in intermediate follicle proportions (p &lt; 0.05). In the FT-CAM group, however, the percentage of primordial follicles stabilized between D1 and D6, showing significantly higher rates than the FT-IVC group on D6 (p = 0.04) and reflecting better preservation of the primordial follicle pool in the FT-CAM group. While apoptotic follicle rates increased in all conditions (D0 vs D6, p &lt; 0.03), they remained significantly lower in the FT-CAM group than in the FT-IVC group on D6 (p = 0.01), confirming superior follicle preservation in CAM-grafted tissue. In primordial follicles, significantly lower levels of p-rpS6 were noted over time in all conditions (D0 vs D6, p &lt; 0.009), but there was a significant shift in FOXO1 to a nuclear localization in the FT-CAM group compared to the FT-IVC group on D1 (p = 0.03), indicating inhibition of follicle activation.

Limitations, reasons for caution

As demonstrated by our results, the CAM model appears to be effective at preserving the follicle pool. However, our study did not investigate the underlying mechanisms behind this improved follicle preservation after thawing.

Wider implications of the findings

Our data confirm that the freezing procedure itself does not cause follicle burnout. Moreover, the CAM model looks to be capable of preserving the follicle pool, hypothetically thanks to rapid revascularization and circulating embryonic anti-Müllerian hormone.

Trial registration number

Not applicable

P-483 Improving in vitro culture of isolated human ovarian primordial-primary follicles by adding adipose derived stem cells

Study question

Could adipose derived stem cells (ADSc) secrete survival- and growth-promoting factors able to improve in vitro culture (IVC) of human isolated follicles?

Summary answer

Co-encapsulation of isolated human primordial-primary follicles with ADSc enhances follicular survival, growth and maturation after 7 days of IVC.

What is known already

The ability to obtain in vitro mature oocyte from earliest follicular stage may help to preserve fertility in female cancer patients.

Unfortunately, human primordial follicles show low rates of growth in vitro. The only study that obtained mature human oocytes from primordial follicle used an IVC multi-step method with a success rate lower than 1% and abnormal polar body.

Recently, several studies have shown that, in mice, ADSc promote survival, antrum formation and oocyte maturation in vitro by secreting factors important for follicular development.

To our knowledge, no IVC studies on human ovarian follicles have been attempted using ADSc.

Study design, size, duration

Fragments of frozen-thawed human ovarian tissue (n = 5) have been mechanically and enzymatically digested to isolate primordial-primary follicles. Eight-to-ten isolated unilaminar follicles have been embedded in alginate-matrigel, half with 20.000 ADSc and half alone. Alginate beads were then cultured in vitro for 7 days. At day (D) 7, we compared isolated follicles co-cultured with ADSc to isolated follicles cultured alone.

Participants/materials, setting, methods

Every two days, IVC medium has been collected to perform hormonal (estradiol, progesteron, anti-Müllerian hormone, androgen, dehydroepiandrosterone) and growth factors measurement (VEGF, bFGF, IGF, HGF) by enzyme-linked immunosorbent assay (ELISA) to study follicle and ADSc interactions. Follicle diameter have been measured at D0 and at D7 of IVC. At D0 and at the end of the IVC (D7), follicle viability (live dead assay) and ultrastructure (transmission electron microscopy [TEM]) have been investigated.

Main results and the role of chance

A total of 373 unilaminar follicles were obtained after enzymatic isolation. At the end of IVC the percentage of viable follicles (with &lt;10% of dead granulosa cells) was found to be significantly higher in follicles co-cultured for 7 days with ADSc (63.3%) compared to follicles in vitro cultured alone (45.5%) (p &lt; 0.01). A significant increase in follicle size was observed in both groups after culture (p &lt; 0.0001). This increase was statistically higher in follicles co-cultured with ADSc than follicles cultured alone (p &lt; 0.005), reflecting better follicle growth in the follicle-ADSc group. Preliminary results by TEM show ADSc did not affect the ultrastructure of isolated follicles after 7 days of IVC.

Limitations, reasons for caution

As demonstrated by our results, ASCs appears to improve IVC conditions and boost follicle activation and survival preserving the follicle ultrastructure. Our study, however, did not investigate the underlying mechanisms behind this improved follicle growth and survival after IVC.

Wider implications of the findings

Co-encapsulation of human unilaminar follicles with ADSCs promotes early-stage ovarian follicle development and survival, possibly because of bidirectional interactions between follicles and ADSCs. This represents a promising first step for fertility preservation in female cancer patients who cannot benefit from cryopreserved ovarian tissue transplantation.

Trial registration number

not applicable

Conservative Management of Uterine Fibroid-Related Heavy Menstrual Bleeding and Infertility: Time for a Deeper Mechanistic Understanding and an Individualized Approach

(1) Background: Uterine fibroids are the most common form of benign uterine tumors, causing heavy menstrual bleeding (HMB), pelvic pain, infertility and pressure symptoms. Almost a third of women with uterine fibroids seek treatment. The objective of this review is to understand the mechanisms linking fibroids to these symptoms and evaluate different options for their management, particularly the place of gonadotropin-releasing hormone (GnRH) antagonist. (2) Methods: We gathered the most recent and relevant papers on the main fibroid-related symptoms and medical and surgical therapy for their treatment. Those reporting use of oral GnRH antagonists were investigated in detail. (3) Results: The mechanisms explaining myoma-related HMB and infertility were reviewed, as they are essential to a deeper mechanistic understanding and oriented approach. The choice of treatment depends on the number, size, and location of fibroids, and is guided by the patient’s age and desire to preserve her fertility. Economic impacts of myomas in terms of direct costs, lost workdays, and complications were found to be significant. Medical, surgical, and non-surgical strategies were analyzed in this context. Novel medical approaches with GnRH antagonist were explored and found to represent an effective new option. (4) Conclusion: The need for alternatives to surgical intervention is very real, especially for women seeking to preserve their fertility. New options now exist, with GnRH antagonists proven to treat fibroid symptoms effectively, opening the door to novel strategies for the management of myomas.

O-192 Modulating hypoxia and oxidative stress in human ovarian tissue xenografts using adipose tissue-derived stem cells

Study question

To investigate whether adipose tissue-derived stem cells (ASCs) modulate hypoxia and oxidative stress in human ovarian tissue transplants to reduce early follicle loss.

Summary answer

ASCs protect the follicle pool by mitigating the hypoxia-related response through HIF1↑ signaling in human xenografts and enhancing revascularization by ensuring faster tissue reperfusion.

What is known already

ASCs are known for their angiogenic potential and capacity to boost angiogenesis by secreting growth factors and differentiating into vessels in numerous models of wound healing in regenerative medicine. In a 2-step ovarian tissue xenotransplantation involving grafting inside a fibrin scaffold two weeks prior to transplantation, ASCs reduced follicle loss after short- and long-term grafting, as well as abnormal follicle activation, by increasing reoxygenation and revascularization in human xenografts.

Study design, size, duration

Prospective experimental study. Cryopreserved ovarian cortex from five adult women was transplanted to 30 nude mice, with or without ASCs (ASC group; OT group). Ovarian grafts were retrieved on days 3 (n = 5), 10 (n = 5) and 21 (n = 5). One piece of ovarian tissue per patient was fixed for analysis after thawing to serve as non-grafted controls.

Participants/materials, setting, methods

The 10 animals grafted for 21 days underwent in vivo microdialysis evaluation to investigate direct reactive oxygen species (ROS) kinetics. Analyses of ovarian grafts at all time points and non-grafted controls included immunolabeling for double CD34 (revascularization by host and graft components), immunofluorescence for HIF1α (hypoxia-related response), Nrf2 (oxidative stress-related response) and 8OHdG (oxidative stress-related DNA damage), and gene expression (RT-qPCR) for VEGF-A (neoangiogenesis), SOD2 (antioxidant activity) and Nrf1 (mitochondrial biogenesis).

Main results and the role of chance

ROS peaked sooner in the ASC group (day 2, p &lt; 0.0001) than the OT group (day 10, p = 0.01) after grafting, indicating earlier tissue reperfusion. Total vascularization was stable in the ASC group at all time points, but lower in the OT group 3 days after grafting (p = 0.01) due to a drop in both host and graft vascular components. HIF1α expression, detected mainly in follicles, was significantly lower in primordial follicles in the ASC group than the OT group on days 3 (p = 0.008) and 10 (p = 0.01). VEGF gene expression rose significantly (around 40x) in both groups on day 3 and persisted significantly longer in the ASC group (10 days) than the OT group (3 days) (p = 0.04), emphasizing the role of ASCs as enhancers of proangiogenic factors. There was no upturn in the oxidative stress-related response (Nrf2 pathway) nor DNA damage (8OHdG) to follicles in any of the grafted groups over time, while a modest increase in both markers was observed only in the stroma after 21 days. Neither was there any major increase in SOD2 and Nrf1 gene expression, suggesting no significant activation of the Nrf2 pathway for cytoprotection from oxidative stress.

Limitations, reasons for caution

Although Nrf2 signaling activation was detected in human granulosa cell cultures in increasing ROS concentrations, our findings did not confirm its role in tissue damage modulation after ovarian tissue transplantation. Further studies may evidence the involvement of other pathways that modulate oxidative stress after transplantation.

Wider implications of the findings

The role of ASCs in protecting the follicle pool appears to be related to a decrease in hypoxia and faster ovarian graft revascularization and reperfusion, sustained by an increase in VEGF for a longer period after grafting. There was no evidence of oxidative stress-related damage, irrespective of the transplantation strategy.

Trial registration number

 

O-179 Safety of ovarian tissue cryopreservation and transplantation in patients with central nervous system cancers

Study question

Is cryopreserved ovarian tissue transplantation safe in patients with central nervous system (CNS) tumors?

Summary answer

Cancer cell contamination was not detected in any ovarian samples from patients with CNS tumors by histological analysis, immunohistochemistry, molecular biology or long-term xenotransplantation.

What is known already

Frequently encountered CNS cancers in childhood include astrocytoma, medulloblastoma, ependymoma, glioblastoma and germinoma. CNS tumors have the capacity for extraneural metastases in 0.5-18% of cases. There are two publications reporting metastases to patients’ ovaries from medulloblastoma.

Study design, size, duration

Prospective experimental study conducted in an academic gynecology research laboratory using frozen-thawed ovarian tissue from 20 patients suffering from 6 types of CNS tumors, including the most common forms mentioned above and primitive neuroectodermal tumors (PNET). Five-month xenotransplantation was performed to severe combined immunodeficient (SCID) mice.

Participants/materials, setting, methods

Cryopreserved ovarian tissue from 20 patients with CNS cancers was thawed and analyzed for minimal disseminated disease and long-term xenografting to immunodeficient mice. The presence of malignant cells was assessed in both cryopreserved and xenografted ovarian tissue using histological analysis, immunohistochemistry for disease-­specific markers (neuron-specific enolase [NSE] and glial fibrillary acidic protein [GFAP]) and reverse transcription droplet digital polymerase chain reaction (RT-ddPCR) for quantification of GFAP gene amplification.

Main results and the role of chance

No malignant cells were detected in frozen-thawed ovarian tissue from any of the patients by histology, immunolabeling for NSE and GFAP, RT-ddPCR for detection of GFAP gene amplification or xenotransplantation to SCID mice. One patient successfully underwent frozen-thawed ovarian tissue transplantation, resulting in the birth of 3 healthy children, but suffered a recurrence of her PNET 6 years after reimplantation and sadly died. Scrupulous analysis of her remaining frozen tissue showed no infiltration by malignant cells, neither after thawing nor long-term xenotransplantation. No relationship was ever established between the patient’s relapsed cancer and reintroduction of her cryopreserved ovarian tissue. The risk of reseeding cancer cells when transplanting ovarian tissue in patients with CNS cancers can therefore be considered low.

Limitations, reasons for caution

The risk of ovarian metastases cannot be completely ruled out for any type of tumor because we cannot analyze the actual fragments that will be reimplanted.

Wider implications of the findings

Our results indicate that the risk of disseminated disease in ovarian tissue from CNS patients is minimal. This is useful information for doctors when counseling women looking to undergo ovarian tissue transplantation.

Trial registration number

Not applicable

Can Endometriosis-Related Oxidative Stress Pave the Way for New Treatment Targets?

Endometriosis is a disease of reproductive age characterized by chronic pelvic pain and infertility. Its pathogenesis is complex and still partially unexplained. However, there is increasing evidence of the role of chronic inflammation, immune system dysregulation, and oxidative stress in its development and progression. The latter appears to be involved in multiple aspects of the disease. Indeed, disease progression sustained by a hyperproliferative phenotype can be related to reactive oxygen species (ROS) imbalance, as numerous experiments using drugs to counteract hyperproliferation have shown in recent years. Chronic pelvic pain is also associated with cell function dysregulation favoring chronic inflammation and oxidative stress, specifically involving macrophages and mast cell activation. Moreover, there is increasing evidence of a role for ROS and impaired mitochondrial function not only as deleterious effectors of the ovarian reserve in patients with endometriomas but also in terms of oocyte quality and, hence, embryo development impairment. Targeting oxidative stress looks to be a promising strategy to both curb endometriotic lesion progression and alleviate endometriosis-associated symptoms of chronic pain and infertility. More investigations are nevertheless needed to develop effective therapeutic strategies for clinical application.

Ovarian tissue damage after grafting: systematic review of strategies to improve follicle outcomes

Frozen-thawed human ovarian tissue endures large-scale follicle loss in the early post-grafting period, characterized by hypoxia lasting around 7 days. Tissue revascularization occurs progressively through new vessel invasion from the host and neoangiogenesis from the graft. Such reoxygenation kinetics lead to further potential damage caused by oxidative stress. The aim of the present manuscript is to provide a systematic review of proangiogenic growth factors, hormones and various antioxidants administered in the event of ovarian tissue transplantation to protect the follicle pool from depletion by boosting revascularization or decreasing oxidative stress. Although almost all investigated studies revealed an advantage in terms of revascularization and reduction in oxidative stress, far fewer demonstrated a positive impact on follicle survival. As the cascade of events driven by ischaemia after transplantation is a complex process involving numerous players, it appears that acting on specific molecular mechanisms, such as concentrations of proangiogenic growth factors, is not enough to significantly mitigate tissue damage. Strategies exploiting the activated tissue response to ischaemia for tissue healing and remodelling purposes, such as the use of antiapoptotic drugs and adult stem cells, are also discussed in the present review, since they yielded promising results in terms of follicle pool protection.

Ovarian tissue cryopreservation and transplantation in patients with central nervous system tumours

STUDY QUESTION

Is there a possibility of reseeding cancer cells potentially present in frozen ovarian tissue from patients with central nervous system (CNS) tumours?

SUMMARY ANSWER

Malignancy reseeding in cryopreserved ovarian tissue from 20 patients with CNS tumours was not detected by histology, immunohistochemistry (IHC), molecular biology or xenotransplantation.

WHAT IS KNOWN ALREADY

Ovarian metastasis potential has been documented in patients with leukaemia, borderline ovarian tumours, advanced breast cancer and Ewing sarcoma. However, data on the safety of transplanting frozen-thawed ovarian tissue from cancer patients with CNS tumours are still lacking.

STUDY DESIGN, SIZE, DURATION

This prospective experimental study was conducted in an academic gynaecology research laboratory using cryopreserved ovarian cortex from 20 patients suffering from CNS tumours. Long-term (5 months) xenografting was performed in immunodeficient mice.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Subjects enrolled in the study were suffering from one of six types of CNS tumours including medulloblastoma, ependymoma, primitive neuroectodermal tumours, astrocytoma, glioblastoma and germinoma. The presence of malignant cells was investigated with disease-specific markers for each patient in cryopreserved and xenografted ovarian tissue by histology, IHC via expression of neuron-specific enolase (NSE) and glial fibrillary acidic protein (GFAP), and reverse transcription droplet digital polymerase chain reaction (RT-ddPCR) for quantification of GFAP and ENO2 gene amplification.

MAIN RESULTS AND THE ROLE OF CHANCE

Serial sections of cryopreserved and xenografted ovarian tissue from 20 patients showed no malignant cells by histology. All samples were negative for NSE and GFAP, although these neural markers were expressed extensively in the patients' primary tumours. Analysis by RT-ddPCR revealed no cancer cells detected in cryopreserved and xenografted ovarian fragments from subjects with astrocytoma, ependymoma, glioblastoma or medulloblastoma. Taken together, the study found no evidence of malignancy seeding in frozen-thawed and xenotransplanted ovarian tissue from patients affected by CNS cancers.

LIMITATIONS, REASONS FOR CAUTION

This analysis cannot guarantee complete elimination of disseminated disease from all cryopreserved ovarian cortex, since we are unable to examine the fragments used for transplantation.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to be conducted in patients with CNS cancers undergoing ovarian tissue cryopreservation and transplantation, and clearly demonstrates no tumour seeding in their frozen-thawed and xenografted tissue. This information is vital for doctors to provide patients with meaningful and accurate advice on the possibilities and risks of ovarian tissue reimplantation.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique-the Excellence of Science (FNRS-EOS), number 30443682 awarded to M.-M.D. and T.Y.T.N., FNRS grant number 5/4/150/5 and FNRS-PDR Convention grant number T.0077.14 awarded to M.-M.D., grant 2018-042 from the Foundation Against Cancer awarded to A.C., and private donations (Ferrero, de Spoelberch). The authors declare no competing financial interests.

TRIAL REGISTRATION NUMBER

N/A.

Modulating hypoxia and oxidative stress in human xenografts using adipose tissue-derived stem cells

OBJECTIVE

To investigate whether adipose tissue-derived stem cells (ASCs) modulate hypoxia and oxidative stress in human ovarian tissue transplants.

DESIGN

Prospective experimental study SETTING: Gynecological research unit in a university hospital PATIENT(S): Cryopreserved ovarian cortex from 5 adult women.

INTERVENTION(S)

Thirty mice were grafted with frozen-thawed human ovarian tissue, with or without ASCs (2-step/ASCs+ovarian tissue [OT] group and OT group). The ovarian grafts were retrieved on days 3 (n = 5), 10 (n = 5), and 21 (n = 5). The 10 animals grafted for 21 days underwent in vivo evaluations using microdialysis. One piece of ovarian tissue per patient was fixed for analysis after thawing (non-grafted controls).

MAIN OUTCOME MEASURE(S)

Direct reactive oxygen species were collected every second day after grafting by means of microdialysis. Analyses of ovarian fragments included immunolabeling for double CD34 (revascularization by host and graft components); immunofluorescence for hypoxia-inducible factor 1α (hypoxia-related response), nuclear factor erythroid 2-related factor 2 (oxidative stress-related response), and 8-hydroxy-deoxyguanosine (oxidative stress-related DNA damage); and gene expression (quantitative reverse transcription polymerase chain reaction) for vascular endothelial growth factor-A (neoangiogenesis), superoxide dismutase 2 (antioxidant activity), and nuclear respiratory factor 1 (mitochondrial biogenesis).

RESULT(S)

Reactive oxygen species peaked earlier in the ASC group (day 2) compared with that in the OT group (day 10) after grafting. Total vascularization was stable in the ASC group at all time points, while it was lower in the OT group 3 days after grafting. Hypoxia-inducible factor 1α expression, also detected in non-grafted controls, was significantly lower in the ASC group than in the OT group on days 3 and 10. The increase in VEGF gene expression lasted significantly longer in the ASC group than in the OT group. There was no significant upturn in the oxidative stress-related response (nuclear factor erythroid 2-related factor 2 pathway) or oocyte DNA damage (8-hydroxy-deoxyguanosine) in any of the grafted groups.

CONCLUSION(S)

Use of ASCs allows faster ovarian graft reperfusion and mitigates the hypoxia-related response through rapid revascularization, sustained by prolonged increase in vascular endothelial growth factor after grafting. No evidence of oxidative stress-related damage was detected irrespective of the transplantation strategy.

Fertility Preservation: The Challenge of Freezing and Transplanting Ovarian Tissue

Cancer treatments are increasingly effective, but can result in iatrogenic premature ovarian insufficiency. Ovarian tissue cryopreservation is the only option available to preserve fertility in prepubertal girls and young women who require immediate chemotherapy. Ovarian tissue transplantation has been shown to restore hormonal cycles and fertility, but a large proportion of the follicle reserve is lost as a consequence of exposure to hypoxia. Another crucial concern is the risk of reimplanting malignant cells together with the grafted tissue. In this review, the authors advance some challenging propositions, from prevention of chemotherapy-related gonadotoxicity to ovarian tissue cryopreservation and transplantation, including the artificial ovary approach.

Can frozen-thawed human ovary withstand refreezing-rethawing in the form of cortical strips?

PURPOSE

The aim of this study was to elucidate whether ovarian tissue is able to withstand a double freezing-thawing procedure.

METHODS

Human ovarian cortical biopsies from 4 thawed whole ovaries were divided into 4 experimental subgroups: (a) frozen-thawed non-grafted group, (b) frozen-thawed xenografted group, (c) refrozen-rethawed non-grafted group, and (d) refrozen-rethawed xenografted group. Xenografting was performed using 8 severe combined immunodeficient mice for a total duration of 21 days. The following analyses were conducted: classic hematoxylin and eosin staining, Ki67 immunolabeling, transmission electron microscopy, Masson's green trichrome, and double CD34 immunostaining.

RESULTS

Morphologically normal preantral follicles were detected in all groups. We observed a dramatic decline of more than 65% in early preantral follicle survival rates after grafting of both frozen-thawed (p < 0.0001) and refrozen-rethawed (p < 0.0001) ovarian tissue. However, mean follicle densities remained comparable between the frozen-thawed and refrozen-rethawed non-grafted groups, as well as both grafted groups. Equivalent proportions of proliferating early preantral follicles were identified in frozen-thawed and refrozen-rethawed samples, whether the tissue was grafted or not. Furthermore, we did not observe any significant difference in atretic follicle rates between any of the four groups, and the ultrastructural quality of follicles appeared unaffected by the refreezing procedure. Similar proportions of fibrosis were noted in the frozen-thawed and refrozen-rethawed groups, irrespective of grafting. Finally, no significant differences were witnessed in terms of vascularization.

CONCLUSION

We were able to demonstrate, for the first time, that refrozen-rethawed ovarian tissue has the same functional characteristics as frozen-thawed ovarian tissue.

Long-Term Advantages of Ovarian Reserve Maintenance and Follicle Development Using Adipose Tissue-Derived Stem Cells in Ovarian Tissue Transplantation

(1) Background: Ovarian tissue transplantation with adipose tissue-derived stem cells (ASCs) has been shown to enhance graft vascularization and increase follicle survival after a short interval of 7 days. The aim of the present study was to investigate their long-term effects on primordial follicle pool maintenance and follicle development. (2) Methods: A total of 14 severe combined immunodeficient (SCID) mice were grafted with frozen-thawed human ovarian tissue with or without ASCs. Blood was taken monthly in order to quantify the anti-Müllerian hormone (AMH) and estradiol. After 6 months, all the grafts were retrieved and sent for histology and immunolabeling (AMH, AMH receptor II, estrogen receptors α and β, and c-kit/kit ligand). (3) Results: A significant upturn was observed in AMH and estradiol plasma levels 4 months after transplantation in both grafted groups. The primordial follicle pool was better preserved in the ASC group (41.86 ± 28.35) than in the standard transplantation group (9.65 ± 17.6, p < 0.05) compared to non-grafted controls (124.7 ± 140). (4) Conclusions: The use of ASCs prior to ovarian tissue transplantation yielded a larger primordial follicle pool and more physiological follicle distribution after long-term grafting. These findings suggested that ASC use might extend the ovarian tissue lifespan.

Adipose tissue-derived stem cells boost vascularization in grafted ovarian tissue by growth factor secretion and differentiation into endothelial cell lineages

Adipose tissue-derived stem cells (ASCs) have multilineage differentiation potential, proangiogenic properties, and the ability to enhance vascularization in xenografted human ovarian tissue. The aim of the present study was to identify the mechanisms behind the proangiogenic effects of ASCs. For this purpose, severe combined immunodeficient (SCID) mice were grafted with frozen-thawed human ovarian tissue. ASCs were labeled by lentiviral transfection for expression of enhanced green fluorescent protein (eGFP), and human ovarian tissue was grafted using a previously described two-step procedure. In the control group, ovarian tissue was transplanted using the standard one-step approach. Samples were collected and analyzed after 7 days. Detection of the eGFP antigen by immunofluorescence showed ASCs surrounding and infiltrating ovarian tissue grafts. Significantly higher vessel density was observed in the ASC group (P = 0.0182 versus control) on Day 7. Co-expression of eGFP, CD34 and CD31 was demonstrated in human vessels, confirming ASC differentiation into human endothelial cell lineages. Increased gene expression of vascular endothelial growth factor (VEGF) was also shown in the ASC group (P = 0.0182 versus control). Immunohistochemistry targeting anti-human VEGF revealed significantly higher expression levels in the ASC group (P = 0.033 versus control), while VEGF and eGFP immunofluorescence showed greater growth factor expression in areas surrounding ASCs. In conclusion, ASCs differentiate into human vessels and promote secretion of VEGF when transplanted together with human ovarian tissue to SCID mouse peritoneum using a two-step ovarian tissue grafting procedure. This is a promising step towards potentially improving ovarian tissue quality and lifespan. Long-term studies should be conducted to investigate ASC safety and efficacy in the context of ovarian tissue transplantation.

Two-step transplantation with adipose tissue-derived stem cells increases follicle survival by enhancing vascularization in xenografted frozen-thawed human ovarian tissue

STUDY QUESTION

Do adipose tissue-derived stem cells (ASCs) enhance vascularization and follicle survival in xenografted ovarian tissue using a two-step transplantation approach?

SUMMARY ANSWER

Higher rates of oxygenation and vascularization of ovarian tissue, as well as increased follicle survival rates, were detected in the early post-grafting period.

WHAT IS KNOWN ALREADY

ASCs have multilineage differentiation potential, proangiogenic properties and enhance vascularization in a peritoneal grafting site. Some studies suggest that using ASCs may improve ovarian tissue quality by enhancing graft angiogenesis.

STUDY DESIGN, SIZE, DURATION

A total of 15 severe combined immunodeficient (SCID) mice were intraperitoneally grafted with frozen-thawed human ovarian tissue (OT) from five different patients. A peritoneal transplantation site had been previously prepared in a first step using either empty fibrin (Fi+OT group [n = 5]) or ASC-loaded fibrin (Fi/ASCs+OT group [n = 5]) for 14 days prior to grafting. Five mice underwent the standard one-step transplantation procedure and served as controls (OT group). Lithium phthalocyanine (LiPc) crystals were inserted into all grafted human ovarian tissue before transplantation. Levels of partial pressure of oxygen (pO2) in grafts were monitored in vivo by electron paramagnetic resonance (EPR) oximetry on Days 3 and 7. Samples for histology and immunohistochemistry (IHC) were collected after euthanizing the mice on Day 7 following EPR. One piece of ovarian tissue per patient was fixed for analysis to serve as non-grafted controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Prospective experimental study conducted at the Gynecology Research Unit, Université Catholique de Louvain. All materials were used to perform pO2 measurements (EPR oximetry), histological (haematoxylin and eosin staining), immunohistochemistry (anti-mouse and human double CD34 and anti-human Ki-67) and TUNEL analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

A significant increase in pO2 was observed in all groups between Days 3 and 7 (P < 0.001). A significantly higher pO2 level was observed in the Fi/ASCs+OT group compared to the OT group on Day 7 (P = 0.028). Total CD34-positive vessel area on Day 7 was greater in the Fi/ASCs+OT group than in any other group (vs non-grafted group: P = 0.0014; vs OT group: P = 0.013; vs Fi+OT group: P = 0.018). Primordial follicle survival rates after grafting were higher in the Fi/ASCs+OT group than in the OT (P = 0.0059) or Fi+OT groups (P = 0.0307). TUNEL-positive follicle percentages after grafting were significantly lower in the Fi/ASCs+OT group than in any other grafted tissue (vs OT group: P = 0.045; vs Fi+OT group: P = 0.0268). Percentages of Ki-67-positive primordial follicles were significantly higher in all grafted groups compared to non-grafted tissue controls (P < 0.01).

LIMITATIONS REASONS FOR CAUTION

As demonstrated by our results, the proposed two-step ovarian tissue transplantation procedure using ASCs enhances vascularization in the early post-grafting period, leading to increased follicle survival rates and decreased apoptosis. However, mechanisms involved in the proangiogenic behavior of ASCs remain to be elucidated.

WIDER IMPLICATIONS OF THE FINDINGS

Our results suggest that the proposed transplantation procedure with ASCs is a promising step towards potentially solving the problem of massive follicle loss after ovarian tissue grafting.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS-PDR Convention T.0077.14, grant Télévie No. 7.6515.16 F to DDM and grant 5/4/150/5 awarded to MMD and CAA is research associate, FRS-FNRS), Fonds Spéciaux de Recherche, Fondation St Luc, and Foundation Against Cancer, and donations from the Ferrero family.